This is a program/project grant to support basic research in areas of molecular and cellular biology which directly relate to the ways in which viruses change normal cells into cancer cells. Over the next five years, our program envisages the close working together of several major research divisions (1) Tumor Virus Section, (2) Cell Culture and Virus Preparation Section, (3) Protein Synthesis Section, (4) Mammalian Cell Genetics Section, (5) Cell Biology Section, (6) Electron Microscopy Section, (7) Nucleic Acid Chemistry Section, (8) Protein Chemistry Section, (9) Molecular Genetics Section, (10) Central Research Services Section, (11) Meetings and Immunogenetics Workshop Section.